循环荷载下饱和黄土不排水强度退化规律试验与理论研究

Testing and theoretical study of undrained shearing strength of saturated loess under cyclic loading

循环荷载作用下饱和黄土的不排水抗剪强度会出现退化。退化主要由两方面的原因引起:一是超孔隙水压力的产生而导致有效应力的降低;二是塑性残余变形的累积导致土体内部结构发生了改变。首先基于静三轴不排水剪切试验结果,提出了饱和黄土不排水强度比随超固结比以及初始剪切变形变化规律的拟合公式。在此基础上,引入似超固结比的概念来考虑超孔隙水压力的影响,应用拟合公式来考虑剪切变形的影响,最终推导出了饱和黄土不排水强度的退化公式,与试验结果的对比证明了理论公式预测结果的合理性。

The un-drained shearing strength of saturated loess will degenerate under cyclic loading. This degeneration is attributed to two reasons, the first one is the reduction of effective pressure due to the increment of super pore pressure; another one is the change of soil＇s structure attribute to the cumulated of plastic shearing strain. Firstly, on the basis of the undrained shearing tests results, two formulations are given which include undrained strength ratio versus overconsolidation ratio and undrained strength ratio versus initial shearing strain. Then, the quasi-overconsolidation ratio is introduced to consider the effect of super pore pressure; and the fitting formulation is applied to consider the influence of shearing strain. The degenerated formulation of undrained strength of saturated loess is deduced at last; and its reasonableness is proved by the test results.